Excessive Rutting on Taxiway A at Sacramento International Airport — ``Possible Causes and Remedies''

Rutting of flexible pavement is a load-induced phenomenon. It is caused by a combination of densification and shear deformation of any layer of the pavement structure. Severe rutting was observed on the Taxiway A at the Sacramento International Airport. The Runway 16R-34L and associated taxiways at the airport were originally constructed in 1965–66 and were placed in operation in 1967. The entire airfield received a strengthening overlay in 1979 and a second strengthening overlay in 1995. The pavement structure consists of 10 inches of asphalt concrete, 12 inches of crushed gravel base course and 12 inches of subbase. Taxiway A north of Taxiway Y exhibited severe rutting in excess of 2.5 inches. This section of taxiway is exposed to slow moving aircraft and is built on a low strength subgrade soil with a CBR of about 3. This section was exposed to high water table prior to drainage improvements in the early 1990's. There was no pavement subdrain system installed at this site. A visual pavement condition survey in 1992 indicated severe rutting in the same section of the Taxiway A. This section was rehabilitated by milling the existing pavement to a depth of about two inches and resurfacing with four inches of asphalt concrete. The 1993–94 rehabilitation work did not perform well, and the rutting recurred. The recurrence of very severe rutting observed in 2002 indicated that the rutting may have been caused by a combination of many factors, and milling and resurfacing will not correct the problem.